Built-up cellular structure and method of making the same



Jan. 28, 1936. H. N. ArwooD l 2,029,049

BUILT-UP CELLULAR STRUCTURE AND METHOD OF MAKING THE SAME Filed July s1,1954 Patented Jan.I 28, 1936 UNITED STATES PATENT OFFICE BUILT-UPCELLULAR STRUCTURE AND METHOD OF MAKING THE SAME 8 Claims.

This invention relates to a built up cellular structure and method ofmaking the same.

'I'he object of the-invention is to provide a composite cellularstructure, the component rts of which may be readily fabricated to forma built up structural unit which is light in weight and. strong anddurable in construction, and which may be used with good results as abeam or strut member in theconstruction of buildings or as a landing o`rtake-oi oat for aircraft and for Various other purposes.

A further object of the invention is to provide a structural u nitincluding a plurality of laminated tubular members preferablyimpregnated with rubber and disposed in superposed layers with thetubular members of one layer arranged to break-joint with the tubularvmembers of an adjacent layer, the tubular members of each layer beingbonded together and to the tubular e the figures of the drawing:

Figure 1 is a side elevation showing the manner of coiling or Wrappingthe wood veneer strips on a mandrel to form one of the tubular members.

Figure 2-is a perspective view of a gang of said tubular members builtup in superposed layers `and before the outer protective coating orjacket is applied.

Figure 3 is a transverse sectional View of the finished built upstructure or unit.

Figure 4' is an enlarged detail sectional view showing howthe rubbersolution and cellulosic material is forced into the iibers of the wood.Y

Figure 5 is a detail sectional view of one end of the unit showing adiierent manner of closing the tubular members.

Inaccordance with the present invention, I take a thin strip 5 ofnatural wood veneer, preferably birch, and of any desired length, widthand thickness, and preferably immerse this strip in a rubber or latexsolution so as to thoroughly impregnate the bers of the wood and causesaid strip to present a. sticky adhesive surface. The

strip or strips are then dried and wound or coiled around a mandrel 6 ofany desired cross sectional formation to form a tubular cylindricalmember, indicated at 1. The strip or strips 5 are preferably wound inspiral superposed layers 8 with the adjacent edges of the veneer stripsof the foundation layer abutting and with the next succeeding layeroverlapping the founda- V tion layer and in intimate contact therewith.Any desired number of layers of veneer may be vemployed according to thenature of the units desired and the strength and stability necessaryYfor the particular use or purpose.

Inasmuch as the veneer strips are surfaced with rubber, when the stripsare coiled around the mandrel, a tight adhesion between the strips Willresult and the body will be formed, in effect, of alternate layers ofWood and rubber securely bonded together. After the tubular members 'areformed in this manner, they are disposed one above the other to formsuperposed layers 9 with the tubular members of each layer pressed inintimate contact with each other and with the tubular members ofadjacent layers so as to be securely bonded thereto and in intimatecontact therewith. Any number of layers of tubular members may beemployed according to the desired thickness of the unit and the purposefor which it is intended, there being shown, by way of illustration inthe present case, four layers so arranged that the tubular members ofone layer will break-joint with the tubular members of the nextsucceeding layer.

After the tubular members are assembled in the manner described, thestructure thus formed is immersed in an acetone solution containingapproximately five percent, byweight, of solid cellulosic material, suchas cellulose acetate, ni-

trate or cellulose ester, and allowed to remain therein until thecellulosic material entirely covers both the interior and the exteriorof the tubular members so as to form a protective coating or jackettherefor. In some cases it may be found desirable to spray thecellulosic material directly on the tubular members instead of immersingsaid tubular members in the solution. During the immersion of thebuiltupv structure inthe acetone solution, some of the solution Will enterand coat the interior walls of the tubular members and also fill thegaps or spaces l0 bey tween the y several tubular members'. Suitablemandrels are then inserted in the different tubular members so astocause them to retain their 'shape' during vulcanization, which latteris effected by placing the built up structure, with the'inandrels kinthetubular members, between suitable pressing elements which areheated-to the proper temperature and then subjecting said elements toheat and pressure.

Ifgdesired suitable disks or other closure members Il may be insertedinthe open ends of the tubular members either prior or subsequent toimmersing the unit inthe celluliosic plastic material, and in some casesit may be -found desirable to cover the open ends of the tubes, at each`side oi the unit, with astrip of rubberized veneer or other materialI2, as best shown in Figure 5 of the drawing, and which rubberized stripwill, ofcourse, be covered with the cellulosic material.

ll'he application of heatand pressure to the built up structure not onlyserves to vulcanize the rubber and causes it to penetrate thexbers ofthe wood,but also causes the plastic material to flow uniformly overtheexterior of the structural .unit and enter and cover any cracks orinterstices which may not he been filled by the rub- 'ber. The plasticmaterial also provides a smooth hard waterproof finish to the unitthereby \en`- abling the unit to withstand the deleterious actionvarious 'other pm'poses. y "35 While it is ,preferred to impregnate thewood veneer strips with rubber, if desired, in certain cases rand undercertain conditions, the rubber may be omitted and the acetone solutionapplied directly tg the woo'd vene'er either before or after the stripsare wound-on the mandrel and I there-- fore do not desire respect. e

It will, of course, be understood that the strucunits' may be made indifferent sizes and to limit the invention in this shapes sindline-'individuel 'tubiner members or any desired cross-sectionalformation without departing from the spirit of the invention.`

Having thus described ine invention, I claim:

i. A composite-structural unitv comprisingca plurality of" tubularmembers each formed of form witli the wood veneer offadjacent pliesoverlapping, said tubularmembers being lflispos'ed 'in superposed layersyto form a builtsup l structure with the'tubula'r members 'of eachlayer' l engagement with each other. and with the tubular of! adjacentlayers, and an acetone `solution containing cellulosic plastic materialforming coatingv for -the built/up structure.v

2. A composite structural unit comprising a plurality of `tubularmembers' iiisuperposed relation to .forniga built 11p-structure.' a

superposed plies` of woodveneer wound in spiral l 'coatingofcellulosicplasticfmaterial covering the built'up structure-'and intimatelyconnectedewith and peiidedthereto te ronnie. har'i exterior 3.A'compo'site a wpluralityof rubber imprenatedtubular. members l' vdisposed in 'lllll'pwdlayersfwith the tubular members er one 1ere:-

.te breek-Joint with the tubular members of adjacent layers, land Hacoating of cellulosic plastic materIaLIorniing-- a for said unit andbonded.

to the adjacent rubber members.

4. A composite structural funit comprising a plurality of tubularmembers each formed of impregnated itubular laminations of' wood veneerimpregnated 'with rubber, said tubular members being disposed insuperposed layers and arranged to break-joint with the tubular membersof each layer having Hou elastic bonding engagement with each other andwith the tubular members of adjacent layers, anda. coating of cellulosicplastic material entirely 'covering the unit.

5. A composite structural unit comprising a plurality of open-endedtubular memberseach formed of laminationsof woodc veneer disposed inspiral relation and impregnated with rubber, said tubular members beingdisposed in superpos'ed layers and arranged to 'break-joint with thetubular members of each layer having elastic ,bonding engagement .witheach other and with the tubular members of adjacent layers, closures forthe open ends of the tubular members, and a coating -of cellulosicplastic material extending over the .closures and bonded to theoutermost layers of the tubular members to form a hard exterior nishtherefor.

6. A composite structural unit comprising a plurality of o'penendedtubular members each formed of laminations ofwood veneer impreg-".'nated with rubber, said tubular members being disposed in superposedlayers and arranged to breaki-joint with the tubular members of eachlayer having elastic bonding engagement, with each othefand with thetubular members of adjacent layers, a rubber impregnatedreinforcingstrip forming a closure for the open ends of the tubular members, and acoating of cellulosic plas-v tic material covering 'said strip and theoutermost layers of tubular members and lling the space between saidtubular members to'form' va hard exterior iinlsh.

7:- The method of making 'a cellular structural unit which consists inwinding 'a strip of brous materialen a shaping mandrel to form a tubularmember, removing the tubular member from thev mandrel, assemblingseveral of said tubular members in superposed layers to form a built upstructure, applying an acetone solution contain-` ing a small percentageof cellulosic material, to said built up structure, insertingnishingmandrels within `the tubular members and while the finishing mandrels rein place subjecting th built up structure to eat and pressure. i

8 jThe method of making a cellular structural unit whicheconsists inimpregnating a strip of wood veneer withrubber,;-winding the veneerstrip `oria shaping mandrel to `iorm a tubu` lar member, removing thetubular member from' vthe mandrel,assembling several of said/tubu-l larmembers in superposed layers with thetubular members of one layer)arranged to breakjointv with-the tubular members of an adjacentlayertoform a united built up structure, im-

mersing'the built up structure in an acetone so'- lution containing asmall .percentage of cellulosic material, inserting iinishing mandrelswithin the tubular members, and while the finishing rnandrels in saidtubular members .Subjecting uthe built up structure to heat andvpressure to vulcanize the' rubber and cause thegcellulosic material toow evenly over the' surtxe gt the built up structure to. provide a harde ri riinmr'iarn g5 -'isili therefor.

